4/3 Users - How Good is Selective Focus DOF control on 4/3 Cameras?

[payasam]

The Sigma lens has had many buyers, so clearly it is not out of everyone's reach: but $439 was too expensive for me, and at $200 the 25/2.8 was affordable. Ideas like "expensive" and "cheap" are by their nature relative.

My understanding is that the 20/1.7 is for Micro Four Thirds. My E-300 and E-510 are plain old Four Thirds. To me that is sufficient reason to avoid buying that lens.

BillP, early on I said "Out of focus backgrounds are much more difficult to get than on a full frame 35mm camera", and in a later post I quoted this sentence. The word "more" has to do with degree, and perhaps you will agree that "much more difficult" differs from "impossible".

[edit] Jack, I do a fair bit of portrait work, and in it my Leica and FED with 85 and 50 lenses are much to be preferred to my Four Thirds cameras. I cannot go back to film completely, as photo buyers now want digital files and I need to sell enough to keep the wolf from the door. I chose Four Thirds because both cameras and lenses are at least as good as the competition but cost slightly less and, by and large, are slightly smaller also. Full-frame digital equipment is, at this time anyway, beyond my means.

 

[bo_lorentzen]

Jack, nice shot.


Bo

www.bophoto.typepad.com

 

[jsrockit]

*Shakes head* Nobody listen to Zathras...

Does this look like an "up close object"...?

Regards,

Bill

I was specifically talking about the lenses made for u4/3, not a retro fitted fast lens (effectively a telephoto with an adapter on 4/3 due to the crop factor no?)... which I believe your photo was taken with. I apologize, but I use equivilents of 28mm to 50mm lenses only...so I was a little too quick with my declaration.

 

[BillP]

I was specifically talking about the lenses made for u4/3, not a retro fitted fast lens (effectively a telephoto with an adapter on 4/3 due to the crop factor no?)... which I believe your photo was taken with.

No. Where did you get the idea that it was taken with a non-4/3 lens? Furthermore the OP did not specify 4/3 or u4/3, or focal length.

Regards,

Bill

 

[payasam]

jsrockit, it is Jack Conrad who used a non-4/3 lens. No idea which lens BillP used, except that it looks a pretty long one.

 

[NDAv]

DoF calculations assume that you print your picture at an 8x10 size (IIRC) without cropping.

DoF is a nonlinear property of focal length, sensor size, aperture, and print size. So it's usually a good idea to let a calculator do the thinking for you 🙂 : http://www.dofmaster.com/dofjs.html

DoF calculators use sensor size to identify the type of lens. It based on the assumption that the lens mounted in front of the sensor was actually designed for the sensor size. I can understand 4/3 and m4/3 lenses having larger DoF than equivalent lenses on other formats, but I don't see how those larger format lenses could have increased DoF from the 4/3 sensor. If simple sensor cropping can increase DoF, then simply cropping in Photoshop can increase DoF too.

 

[antiquark]

DoF calculators use sensor size to identify the type of lens. It based on the assumption that the lens mounted in front of the sensor was actually designed for the sensor size.

No, the calculators don't care about the brand of lens, only the focal length and aperture.

I can understand 4/3 and m4/3 lenses having larger DoF than equivalent lenses on other formats, but I don't see how those larger format lenses could have increased DoF from the 4/3 sensor.

Actually using the same focal length (in mm) will reduce the DoF on a 4/3 sensor. It's all nonlinear, there is no easy rule. That's why the calculator is so useful.
http://www.dofmaster.com/dofjs.html

If simple sensor cropping can increase DoF, then simply cropping in Photoshop can increase DoF too.

If you cropped in photoshop, then printed to 8x10, then the DoF will actually be reduced. In effect, the cropping process acts like you used lens with a longer focal length.

 

[40oz]

Basically, when you use a crop sensor you are blowing up the images to get to 8x10 far more than you would with say 35mm. This causes areas that would seem to be in acceptable focus at 2" x 3" to now appear out of focus at 8" x 12". The result is that you get a narrower depth of field than you would with the exact same lens and aperture on a larger sensor.

It's easy to see how this works - take an out of focus shot and shrink it way down in photoshop or look at a thumbnail. Hell, look at a negative without a loupe.

There is an issue, however. Small sensors require shorter focal lengths for a given field of view. As the focal length shortens, the difficulty of making a fast lens seems to increase. Crop sensor cameras like the 4/3 system are intended for the casual or "serious amateur" user, not the fine art professional. So you have a Sigma 30/1.4, and I think that might be it for faster than f2.8 normal primes. And while it isn't expensive for some people, it is twice the price of the slower primes for that system. In that context, it's expensive.

 

[gdi]

Here are a couple of examples from a GH1 or G1 (with fast M lenses):